László Detre (originally Dunst) was born in Szombathely on 19 April 1906. His father, Dr. János Dunst, a councillor of the city of Szombathely, died when he was two years old, so he was brought up by his widowed mother. He completed his secondary school studies at the Premontrei Gymnasium in Szombathely, where his interest in natural sciences and mathematics soon became apparent. Between 1924 and 1927, he studied mathematics and physics at the Pázmány Péter University in Budapest as a member of the famous Eötvös College. From 1927, he continued his studies at the Friedrich Wilhelms University in Berlin under the guidance of renowned teachers such as Albert Einstein, Max Planck and Paul Guthnick. He defended his doctoral thesis on the spatial distribution of stars in 1929. After completing his studies, he became an assistant at the Hungarian State Konkoly-founded Astrophysical Observatory at Svábhegy (the official name of our institute at the time) in Budapest.
In 1930, the German Astronomical Society (Astronomischen Gesellschaft) held its general meeting in Budapest, attended by celebrities such as Otto Struve and Arthur Eddington. It was at this time that Eddington had shown that by monitoring the periodic variations of short-period pulsating variable stars, it was possible to detect stellar evolution over a few decades and provide information on the then unknown internal energy source of the stars. László Detre, perhaps thanks to the conference mentioned above, changed his subject of research in 1931 and began to work on RR Lyrae type stars and their period variations. From 1932 onwards, he published articles on the subject, mainly photometric observations, in the then leading journal Astronomische Nachrichten and in the Institute's own series of publications (Mitteilungen). Relatively soon it became clear that periodic variations were generally much more complicated than initially thought. They are also strongly influenced by non-evolutionary effects. In the case of RR Lyrae, one of the most important of these is the so-called Blazhko effect, which manifests itself in secondary amplitude and period changes with a much longer period than the pulsation period. Detre, with his wife Júlia Balázs, the first Hungarian female astronomer, spent many years making photometric observations of RR Lyrae stars, and from these they found many of these stars exhibiting the effect. Although the phenomenon had already been discovered by Sergei Blahko in 1907, it did not receive much attention at the time. The frequent appearance of the effect in RR Lyrae stars, as pointed out by the work of the Detre and Balázs, was a big surprise. For example, the brightest RR Lyrae, the eponym of its class, was shown to exhibit the Blazhko effect. The period variation of Blazhko stars is dominated by the effect, making evolutionary changes almost impossible to track. In the 1950s, the idea that the periodic variation of RR Lyrae stars might be shaped by random factors, which further complicate the task of tracing stellar evolution, was proposed and developed in the 1960s.
László Detre became the Director of the Astronomical Institute in 1943, a post he held until his death. As director, he always kept his Institute and the development of Hungarian astronomy in mind. It was thanks to his relations with the Soviet troops, for example, that the Institute's valuable library survived the invasion without damage. After the Second World War, the international astronomical community became united again, and in 1947 Detre became the first Hungarian member of the International Astronomical Union (IAU). At the IAU General Assembly in 1961, it was decided to launch a new publication, Information Bulletin on Variable Stars (IBVS), to facilitate rapid communication on variable stars. The right of publication and editing was entrusted to the Institute headed by László Detre. The first issue was published later that year and IBVS was edited at the institute until its closure in 2019. Detre also headed the Department of Astronomy at Eötvös University from 1964-1968 and taught thereafter until his death. He had a significant role in introducing the university degree in astronomy in Hungary.
Detre was an excellent and diligent observer. He knew that the telescopes on Svábhegy were becoming less and less suitable for professional astronomical observations due to increasing light pollution: high-mountain, well-equipped telescopes were needed, preferably far away from city lights. In 1962, a 60/90/180 cm Schmidt telescope and in 1966 a 50-cm Cassegrain telescope were put into operation in Piszkéstető. The Schmidt telescope is still one of the 10 largest telescopes of this type in the world. In 1974, he also completed the construction of a 1-m telescope of the Ritchey-Chrétien-Coudé type, although he did not have the chance to see its first light. In 1946 he became a corresponding member of the Hungarian Academy of Sciences. In 1955 he was re-elected as a corresponding member and finally became a full member in 1973. In 1970 he was awarded the State Prize. An asteroid (1538) Detre was named after him. The Eötvös Loránd Physics Society's award for Hungarian astronomers also bears his name. A stamp commemorating the 100th anniversary of his birth was issued by the Hungarian Post Office. Most recently, the Municipality of District XII of Budapest named the new road leading to the Institute after him.